A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that circumstance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. comprising part of, one or several dies) on a substrate (e.g. a silicon wafer) that has a layer of radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
When a pattern feature is applied to a substrate, the applied pattern feature is not always as intended. For example, a property of the pattern feature may deviate (i.e. deviate from an intended or desired property). The property could be, for example, a best focus of the pattern feature, a shape or size of the pattern feature, or a location of the pattern feature on the substrate. Taking the best focus of a pattern feature as an example, the best focus of different pattern features can be different due to, for example, a topography of a surface of the patterning device, a resist effect, or another effect that changes the angular distribution of amplitude/phase of radiation redirected by a pattern feature of a patterning device used to provide the pattern feature on the substrate.
One or more deviations in a property of a pattern feature applied to a substrate (from an intended or desired property, e.g. due to an error in the application of the pattern feature) can result in the construction of a device, of which the applied pattern feature is a part, that does not function as intended, or does not function at all. This is undesirable.
It is desirable to provide, for example, a method of at least partially compensating for a deviation in a property of a pattern feature to be applied to a substrate.